Grab for lifting materials



July 13, 1948. s. PRIESTMAN 2,445,002

I GRAB FOR LIFTING MATERIALS Filed June 10. 1946 ,4 Shets-Sheet 1 /7 yen for 9 42 MK J Attorney y 's H. PRIESTMAN 2,445,002

\ I GRAB FOR LIFTING MATERIALS 4 Sheets-Sheet 2 Filed June 10, 1946 Inventor j d /f filed-man y 3a. ,M I Attorney Filed June 10, 1946 July 13, 1948. V s. H. PRIE STMAN 2,445,502 i GRAB Fon LIF'I'ING MATERIALS 4 Sheats-Sheet 3 Int enter ff. PwBTMA/v Attorney July 13, 1948. r I s H.- PRIESTMAN 4 J GRAB FOR LIFTING MATERIALS Filed June 10, 1946 l 4'Sheets-Sheet 4 MMMA' Attorney Patented July 13, 1948 GRAB FOR LIF'I'lNG MATERIALS Sydney Herbert Priestman, Hull, England, as-

signor to Messrs. Priestman Brothers Limited, Hull, York, England, a company of Great Britain Application June 10, 1946, Serial No. 675,559 /2 In Great Britain June 23, 1945 3 Claims. (Cl. 294112) This invention relates to grabs of a type in which the jaws are adapted to be spread widely apart by the use of lazy-tongs linkage, the opening and closing of the grab being controlled by,

some conditions for the jaws to be pushed inwards from the fully expanded position when the grab is opened and is being lowered upon material to be lifted. This can occur for example when the grab is working upon a sloping face of the material to be lifted in which case the grab as a whole may tend to fall downwards on top of the jaw on the lower side, thus causing it to fold inwards, and nothing which the operator can do by manipulating the. ropes can prevent this. The upper jaw may then also fold in under gravity as the grab tilts.

It is the object of the present invention to overcome this defect which only arises under certain conditions and may not be noticed when such a grab is generally being lowered upon more or less even layers of spoil to be lifted.

According to this invention the grab jaws or v or eyelet attached in a suitable position preferably to the lower link of the outer bay of the lazytongs on its own side of the lazy-tongs linkage. The length of each chain is such that, with the lazy-tongs linkage extended, the chain is stretched between its two end attachments so as to hold the jaw to which it is connected fully open. The jaws cannot therefore be'folded in-l wardly when the grab is fully extended under the pull of the opening rope, but must remain in the digging position when lowered upon the spoil, even if the surface is sloping or irregular. The grab therefore commences to dig with the jaws extended but, as the closing rope is hauled in, the jaws are first turned inwardly toward the cutting position while the chains remain tight, after which the jaws are brought together by collapsing the lazy-tongs linkage'and the chains become slack. The shovelling action of the grab is not therefore interfered with nor is its emciency in any way reduced by the addition of the chains referred to above. Chains are preferably used as they hang down freely when slackened 2 and are not liablev to kink, but in place of chains, ropes or any other suitable connections such as linked rods can of course be used if they are so disposed as not to foul other parts of thegrab structure as they fold.

The invention is illustrated in the accompanying drawings in which:

Figure 1 shows a side elevation,

Figure 2 shows an end view, l I

Figure 3 shows a side elevation in the extended position, and Y r Figure 4 shows a side elevation of a grab in accordance with theinvention, with the lazy linkage closed and the jaws open.

(Each of these first four figures shows a grab of the type having-curved tines for digging fibrous material, such as manure).

Figure 5 shows a side elevation in the closed position, and

Figure 6 a partial side view in the extended position of ,a grab according to the invention with buckets suitable for handling materials suchgas ores,v

Referring first to Figures 1 and,2, the lazytongs linkage has three bays, the upper links a ofthe outer bays having long downwardly extending limbs providing pivots at their ends for brackets c carrying the grab jaws d, which in this example are curved tines supported at spaced intervals apart in crossbars e. These crossbars extend through and beyond the brackets c at each side of the grab.v

The brackets c are pivoted between the jaws to links f at g; The links 1 extend upwardlyand haveslots at h in their upper endsv working over pinsz' projecting from the lower links 7' of the outer baysv of the lazy-tongs in this case. The slotted links 1 carry pairs of sheaves is around which passes the closing rope m. One end of this rope is suitably anchored to a point on the linkage, for example by a tab Z to .the pivot n between links 9' and a as shown. From the tab lthe rope passes round sheave k on one slotted link f across to the corresponding sheave k on the opposite slotted link 1, thence up toa sheave. o turning on pivot pin 1) of the outer joint of thelazy-tongs on that side of the grab head, back from sheave o-to a second sheave k: on the same side of the grab head, across the grab head to a second sheave is on the other side, and then upwardly round a sheave q carried by brackets 1' upon the top middle bay of the lazy-tongs. v

From sheave q the rope m extends up, to the jib as usual. The rope m is called the closing rope. A second rope s called the holding ropeor links of the middle bay of the lazy-tongs are drawn together so causing the lazy-tongs linkage to expand as indicated in Figure 3. On the other hand, if the rope s is slackened while the rope in is pulled up, to take the whole weight, the lazytongs linkage is contracted and the jaws d are brought together as shown in Figure 1. In the closed position the pinsz' are at the bottom of slots h in links 1, these links I being drawn together and pulled up by the tension of rope m. The tines or jaws d are then closed because the brackets have their pivots g drawn up relatively to the pivots 1).

According to this invention chains or ropes w (hereinafter referred to as chains) are provided connected at one end as at z to link a and at the other end as by shacklesy to extensions .x' of one of the brackets 0 beyond the pivots b at each side of the grab. When the jaws are closed by pulling on the closing rope m the chains to han loosely as indicated in Figure 1. When the jaws are opened fully by slackening rope m and pulling ropes, the parts of the linkage and the jaws take up the position shown in Figure 1, in which the links are lettered 0. f and W, the bottom brackets c and the jaws (2 In this position the chains '11) are tight as indicated at 20 so holding the jaws positively in; their fully extended position.

It=is in this position that the grab is lowered upon the heap of spoil to be lifted, and even if the spoil is on a slope or is otherwise uneven, there is no risk that the jaws will fold inwardly under the weight of the grab. For engaging the spoil the closing rope m is now pulled while rope s is slackened, and the first effect is to draw inwardly the sheaves 7c. and links causing the slotted ends h to slide up over pins 2', the jaws being turned inwardly to the cutting position ready for beingbrought together to engage and lift the spoil. The chains w are still tight, but the movements of the links to the extent required are not impeded. In fact in changing from position d of the jaws or tines, the chains w by their tension prevent the lazy-tongs linkage from collapsing upon the jaws and so control the change of position of the linkage. Further pulling on the closing rope m now draws the jaws together to take up a load of spoil, while the chains w become slack, and the parts finally reach position of Figure 1.

For discharging the load of spoil, the closing rope m is paid out to some extent with respect to:the rope 3, allowing the sheaves k to drop with links. f. and brackets 0 under the load on the jaws until the. links and jaws occupy the positions indicated by references f 0 and d in Figure 3. Further paying out of rope 122 while the weight is taken by holding rope 3 causes the linkage to expand and the jaws to open fully as already described and indicated by. the reference letters a f 0 and d in Figure 3, while the chains tighten. as at 'w In-Figuresfi and 6 a grab with buckets suitable for. ore-handling and similar purposes is shown in the closed and open positions respectively; and

the corresponding parts are given reference letters in capitals (A to Z). The jaws when opened to discharge the spoil are lettered D when opened to their maximum spread they are lettered D and when drawn in to the level cutting spreadi they are lettered D Other parts are lettered A and A B and B and so forth to denote their corresponding positions. There are a few casual difierences in construction which may benoted. There are no brackets such as c, Figure 1, as the jaws D are directly pivoted at B to the links A, and at G to links F. In place of pins i engaging. in slots h in links f, Figures 5 and 6'show the links F made with long straight upper ends sliding in guides H which are pivoted atIto' links J The closing rope M and opening rope S areguided and operated in the same way as ropes m and s of Figures 1 and 2. The chains W are also similarly connected and serve the same purpose. It is thought that Figures 5 and 5 can be understood from the description of Figures 1- and 2, and the corresponding lettering without further explanation. Some of the parts of the linkageare only indicated by centre lines or centre points in the cutting position, as at A and J I claim:

1. A grab of the lazy-tongs type comprising a lazy-tongs linkage with downwardly prolonged end link members, a pair of jaws and means pivotally connecting them to said downward prolongations of the end link members, additional links connected to each of such jaws and means providing a slidingconnection for such additional. links with elements of said lazy-tongs linkage. an" opening rope and a closing rope, sheaves on such lazy-tongs linkage about which said opening rope passes, sheaves on said linkage and on said additional. links about which said closing rope passes, extensions associated with said jaws beyond their pivotal connections to the downward prolongations of the end members of the lazy-tongs linkage, and flexible connections between said extensions and the lazy-tongs linkage, saidflexible connectionsbeing of such length as to. hold said jaws fully opened in the expanded position of' said lazy-tongs linkage.

2. Agrab of the lazy-tongs type comprising a lazy-tongs linkage with downwardly prolonged end link members, a pair of jaws and means pivotall connecting them to said downward prolongations of the and link members, additional links connected to each of such jaws'and means providing a sliding connection for such additional links with elements of said lazy-tongs linkage, an opening rope and a closing rope, sheaves on such lazy-tongs linkage about which said opening rope passes, sheaves on said linkage and on said additional links about which said closing rope passes, extensions associated with said jaws beyond their pivotal connections to the downward prolongationsof the end members of the lazytongs linkage, lengths of chain connecting each. ofsaid'extensions to elements of the lazy-tongs linkage, such lengths of chain being so dimensioned that they become tight and hold said jaws full opened in the expanded position of said lazy-tongs linkagewhile it is under the pull of the opening rope.

3. A grab of thelazy-tongs type comprising a lazy tongs linkage with downwardly prolonged end link-members, a pair of jaws and means pivotally connecting them to said downward prolongationsof the end link members, additional links connected to each of such jaws and means providing a sliding connection for such additional links with elements of said lazy-tongs linkage, an opening rope and a closing rope, sheaves on such lazy-tongs linkage about which said opening rope passes, sheaves on said linkage and on said additional links about which said closing rope passes, extensions associated with said jaws beyond their pivotal connections to the downward prolongations of the end members of the lazytongs linkage, lengths of chain connecting each of said extensions to elements of the lazy-tongs linkage, such lengths of chain being so dimensioneci that they become tight and hold said jaws fully opened in the expanded position of said lazy-tongs linkage while it is under the pull of REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 771,597 Atherton Oct. 4, 1904 807,823 Horn Dec. 19, 1905 

